The usual reason is that a person having a ‘Role’ (= available to act in a certain capacity) has contact info and sometimes even identifying info specific to the role. E.g.
- Juan Lopez (a PERSON) lives at ‘calle Lobo 51’ (home), phone number 111111111;
- he is a Nurse (a ROLE), and relating to that, can be found at ‘Bulevar Artigas 1590, Lord Ponsoby 2410, 11600 Montevideo, Uruguay’, plus a work phone 222222222
- he is also a part-time sound-stage designer, and for that purpose, the address is ‘5Q36+XP9, Triunfo, 11900 Montevideo’, and he has another phone for that 3333333333
A different identity for a ROLE is not that common, but it happens - writers and rock stars for example, with performance names and so on.
I’ve been reviewing the demographic model, and working on a new version known as an ‘entity’ model, which for the moment may serve only to indicate how to improve the current one. Other parts of that new model should address some long-standing requirements about modelling resources as well (see the sibling packages in the UML).
It’s not complete, and anyone who is interested should comment - initially on this thread, but we can talk about it in SEC if there is interest.